Constant force spring carrier return mechanism

ABSTRACT

Mechanism for biasing a carrier of a printing apparatus for yielding resisting movement thereof along a defined track extending parallel to a print line from a starting position and for returning the displaced carrier back to the starting position. A frame in the mechanism forms an elongated opening which serves as the track and guides an extension of the carrier for to and fro motion parallel to the print line. Carried by the frame is a pair of biasing members in the form of bowed coiled springs which engage the extension of the carrier and resiliently yield to tabulation of the carrier in one direction parallel to a print line and urge return of the carrier in the other direction to its starting position. A shock absorber is positioned in the track at the starting position for absorbing the inertia of the return movement of the carrier and permitting the carrier to overshoot the starting position as its inertia is absorbed.

CONSTANT FORCE SPRING CARRIER RETURN MECHANISM BACKGROUND OF THE INVENTION The invention relates generally to spring devices and specifically to mechanisms for returning displaceable members such as the print hammers of printing machines to predetermined starting or home positions.

In serial printers, that is, printers that print one character at a time in succession, it is necessary to move paper or other print recording medium with respect to an impacting member. This may be accomplished, as in a common mechanical typewriter, by tabulating a paper carriage past a fixed print position or, as in many well-known electronic printers, by moving an impacting member along a print line while maintaining the paper in a fixed position. Either of these methods requires that the movable member be returned to a starting print position after tabulating along the print line.

A common prior art means for returning the carrier of a displaceable member is to controllably engage the carrier with an electronic motor to thereby drive the carrier back to its starting position. While this approach may prove adequate when but a single displaceable member is to be alternately displaced from and returned to its home position, economic disadvantages are encountered when a plurality of members are to be displaced and returned at random and in variable sequence, such variable sequence requiring a plurality of reversible motors corresponding in number to the number of members to be displaced and returned.

A less expensive method of returning a displaced carrier is with a coiled spring, such as the main spring of a watch, the spring being wound when the carrier is tabulated and released when the carrier is disengaged from the tabulating means to thereby return the carrier to its starting position. As the resisting force ofa coiled spring is not constant throughout the entire tabulating distance, but rather, increases in intensity with tabulation distance, the velocity of the carrier tends to attentuate as tabulation proceeds, unless the force driving the carrier is proportionately increased. Satisfactory results can thus be achieved only in conjunction with intricate and expensive tabulating control devices.

SUMMARY OF THE INVENTION It is accordingly an object of the present invention to provide an inexpensive carrier return spring mechanism that resists the tabulation displacement of a carrier with a substantially constant force over the entire tabulation distance.

It is another object of the invention to combine the components of the mechanism in a modular package, such that the mechanism may be manufactured separately from the printing mechanism and may be easily installed and replaced.

i It is still another object of the invention to provide, as an integral part thereof, a means to absorb the shock of a carrier returning to the starting position.

It is a further object of the invention to provide a carrier return mechanism that may be used in multiples in association with a like number of displaceable members and in conjunctionwith asingle tabulating driving means, such driving means being continuously conditioned for displacing individual ones of the members when coupled therewith, the individual members being returnable to their home positions independently of the driving means. r i i The present invention achieves these and other objectives by combining a constant force biasing member with a frame. The frame has an elongated aperture forming a guiding track in which the biasing'me'mber is engaged with a carrier for tabulation of the carrier along the longitudinal dimension of the frame. A shock absorber carried by the frame, in cooperation with the biasing member to which it is placed in opposition, serves to define a starting position for the carrier and yieldably absorbs the inertia of the returning carrier. The longitudinal dimension of the frame is alignable with the path of travel of the displaceable member and the frame is positionable along such path of travel to bring the carrier into a predetermined starting position relative thereto.

BRIEF DESCRIPTION OF THE DRAWING In order to facilitate a more complete understanding of the invention, a preferred embodiment of the carrier return mechanism will hereinafter be described with reference to the drawing in which:

FIG. 1 is a side view of the preferred carrier return mechanism;

FIG. 2 is a plan view of the mechanism;

I FIG. 3 is a plan view of the mechanism illustrated in FIGS. 1 and 2 but with the top section of the frame removed and also showing the spring members in sub stantially maximum arcuate flexure;

FIG. 4 is a partial plan view similar to FIG. 3 showing the shock absorber section of the mechanism resiliently receiving a returning carrier;

FIG. 5 is a sectional view taken along line 5-5 of FIG. 2;

FIG. 6 is a sectional view taken along line 6-6 of FIG. 2; and

FIG. 7 is a partial perspective view of an embodiment of the invention wherein the displaceable member is a print hammer assembly of a printing machine.

DETAILED DESCRIPTION Referring now to the drawing wherein like reference characters designate identical elements in all of the F igures, and specifically to FIGS. 1-6, the operative elements of the mechanism are all mounted in or upon a molded frame generally indicated at 12 that is prefera: bly composed of a plastic material such as a glass-filled thermoplastic. The frame 12 is constructed of two similar abutting sections 14-14, each substantially rectangular in shape and joined by fasteners 16 at two opposing ends in face-to-face relationship to form the frame. 12. Each section 14 has a carrier accepting sector, such as an elongated aperture 18, longtudinally disposed therethroughnhe apertures each section 14 being aligned to form a guiding track for an extension of the carrier 37 when the sections 14-14 are joined; Two fastening apertures 20 in each section 14 provide open ings through which fasteners may securely attachma mechanism to a printing" machine. As the sections 14 are congruent, much of the remaining portion of the description will speak in turns of one section 14, such as shown in FIGS. 3 and 4, inwhich the other section 14 is removed to expose the operative elements of the mechanism. It will be understood that the characteristics of the section 14 described will be common toboth sections 14-14.

37 back to and through the starting position and into engagement with the shock transmitting member 52, as shown in FIG. 4. Biased against the stop 24 by the compression springs 56, the shock transmitting member 52 resiliently yields to the returning carrier 37, and then urges the carrier 37 back into abutment with the carrier coupler 30 at the starting position. System friction quickly dampens any oscillations of the carrier 37 and it is ready to begin another tabulating displacement.

There are many obvious modifications that one skilled in the art could apply to the preferred embodiment of the invention as heretofore described without departing from the inventive concept residing therein. Thus, having described one example of the invention, the following claims seek to define the inventive concept.

What is claimed is:

1. In a printing machine having a carrier disengageably coupled to a driving means for displacement of the carrier along a print line from a starting position to a terminal position, a mechanism for yieldingly resisting the displacement of the carrier away from the starting position and for returning the displaced carrier thereto, said mechanism comprising:

a frame having two spaced apart parallel guide rails forming a carrier accepting track extending parallel to the print line and for at least as long as the distance from the starting position to the terminal position,

a carrier coupler straddling the rails of said track and guided thereby for displacement therealong and having a surface engageable by the carrier so as to be moved thereby along the track when the carrier is displaced away from the starting position, and

a pair of similar compression type spring members lying in the plane of said frame on opposite sides thereof and each having one end pivotally connccted to said frame and the other end pivotally connected to said carrier coupler, said spring members each having a free length greater than the distance between the pivotal connections of their ends with the frame and the carrier coupler when the carrier coupler is engaged by the carrier in said starting position, said spring members each being arcuately flexible and laterally extendible in the plane of the frame as the carrier moves the carrier coupler away from the starting position along the print line in engagement with the driving means, said spring members yieldingly urging the carrier and carrier coupler back toward the starting position of the carrier with substantially constant force and effectivelytransporting the carrier back to said starting position upon disengagement thereof from the driving means. i

2. A mechanism as defined in claim 1 further comprising a shock abosrber positioned to be engaged by the carrier at the starting position thereof, said shock abosrber beingeffective to statically urge the carrier in opposition to said spring members at the starting position and to resiliently resist overrun of the returning carrier beyond the starting position, said shock abosrber comprising a shock transmitting member guided by said track for displacement therealong and a compression spring statically restrinaed at one end by the frame and seated at the other end on said shock transmitting member 3. In a printing machine havin a carrier disengageably coupled to a driving means for displacement of the carrier along a print line from a starting position to a terminal position, a mechanism for yieldingly resisting the displacement of the carrier away from the starting position and for returning the displaced carrier thereto, said mechanism comprising:

a frame having a carrier accepting track extending parallel to the print line and for at least as long as the distance from the starting position to the terminal position;

a carrier coupler guided by said track for displace ment therealong and having a surface engageable by the carrier so as to be moved thereby along the track when the carrier is displaced away from the starting position;

a spring member having one end pivotally connected to said frame and the other end pivotally connected to said carrier coupler, said spring member having a free length greater than the distance between the pivotal connections of the ends of the spring member with the frame and the carrier coupler when said carrier coupler engages the carrier in said starting position,.said spring member being arcuately flexible and laterally extendible as the carrier moves the carrier coupler away from the starting position along the printline in engagement with the driving means, said spring member yieldingly urging the carrier and carrier coupler back toward the starting position of the carrier with substantially constant force and effectively transporting the carrier back to thestarting position upon disengagement thereof from the driving means, and

a shock absorber positioned to beengaged by the carrier at the starting position thereof, said shock absorber being effective to statically urge the carrier in opposition to said spring member at the starting position and to resiliently resist overrun of the returning carrier beyond the starting position, said shock abosrber comprising a shock transmitting member guided by said track for displacement therealong and a compression spring statically restrained at one end by the frame and seated at the other end on said shock transmitting member.

4. A mechanism as defined by claim 3 wherein said carrier accepting track is characterized by an elongated aperture extending through said frame, an extension of the carrier being inserted therein.

5. A mechanism for biasing an object at a starting position and for returning the object from adisplaced position to the starting position, said mechanism compris mg:

a frame including an aperture with two ends spaced apart at a substantially greater distance than the maximum distance between the displaced position and the starting position of the object, a guideway disposed along the length of said aperture, a stop obstructing said guideway, said stop being disposed at least as far from one end of the guideway as said maximum distance, and a spring anchor pin positioned-on the frame adjacent to the one end ofthe guideway opposite from said stop,

a coupler member displaceably movable within said guideway for guidance alongsaid aperture between said stop and the one end of said guideway opposite from said step, a spring anchor pin carried by the coupler memberiand extending generally parallel to the anchor pin positioned on the frame,

a spring member having the opposite ends thereof pivotally connected to said anchor pins and having a free length greater than the distance between said anchor pins when the coupler member is at said stop, said spring member being operative to yieldingly bias said coupler member against said stops, and

a shock absorber including a shock transmitting member also displaceably moveable within said guidcway for guidance along said aperture on the opposite side of said stop from said coupler memher, said shock absorber including also a compression spring having one end statically disposed against said frame and a free .end positioned in abutment with said shock transmitting member for resiliently receiving the returning object and for urging the object in a direction opposing said spring member and back into said biased starting position.

6. A mechanism as defined in claim wherein said spring member comprises a first spiral spring having an extendible bowed portion projecting outwardly from one side of said frame.

7. A mechanism as defined in claim 6 additionally comprising a second spiral spring similarly having an extendible bowed portion projecting outwardly from an opposite side of said frame from said first spiral spring.

8. A constant force carrier return mechanism including, in combination:

a supporting frame having two parallel guide rails forming a track,

a stop positioned at the same location on each guide rail intermediate the ends thereof, the space between the guide rails and the stops being free of obstruction,

a first coupler member bridging the guide rails and guided for movement thereby along that section of the track on one side of the stops, and a second coupler member similarly bridging the guide rails and guided for movement thereby along that section of the track on the other side of the stops, said first and second coupler members being shaped to engage opposite sides of a carrier introduced into the space between the guide rails and each coupler member being moved by the carrier along that section of the track upon which the coupler member is guided when the carrier moves in the direction of the coupler member and away from the stops,

at least one spring member connected at one end to the first coupler member and connected at the other end to the supporting frame adjacent to the end of the track section along which the first coupler member is movable, each said spring member being spirally wound into a coil for part of the length thereof and exhibiting an arcuate formation having a relatively large radius of curvature when the first coupler member is abutting the stops, the radial curvature of the arcuate formation of each said spring member progressively decreasing as the ends of the spring member approach one another pression spring yieldingly urging the second coupler member against said stops but being effective to yieldingly absorb the inertia of the carrier when the carrier overruns the position of the stops on return motion of the carrier along the track.

9. A constant force carrier return mechanism including, in combination:

a supporting frame having two spaced apart parallel guide rails forming a track,

stops positioned at the same location in the guide rails and cooperating to represent a starting position for a mechanism supporting carrier introduced between the guide rails for displacement in either direction along the track and from one side to the other side of the stops,

a coupler member straddling the guide rails and and being guided thereby for displacement theralong away from said starting position and being engageable and jointly movable by the mechanism supporting carrier when the carrier is displaced along the guide rails in the same direction away from said starting position,

at least one spring member having the middle portion thereof in the form of a spirally wound coil such that when the ends of the spring member are drawn toward one another the middle portion thereof will progressively distend laterally in the form of an arc while accompanied by a progressive decrease in the radius of curvature of the arc such that the spring member resists such change in the are formation with a substantially constant force,

means connecting one end of each such spring member to a fixed support and the other end to the coupler member leaving the balance of the spring member free for said lateral arcuate distention relative to the carrier return mechanism, whereby displacement of the coupler member by mechanism supporting carrier away from the starting position will be opposed by a substantial constant force throughout such movement along the track, and

a shock absorbing assembly including a second coupler member interposed in the path of travel of said mechanism supporting carrier adjacent to said starting position and being jointly movable away from the starting position by the carrier when the carrier on return movement thereof overruns said starting position, and further including resilient means yieldingly resisting any such displacement of said second coupler member caused by the overrun of the carrier and being effective to return the second coupler member and the carrier back to the starting position United States Patent DeGraff et al. 1 1 51 Aug. 7, 1973 1 1 SELF-INTERLOCKING KEYBOARD 3,270,853 9/1966 Gerjets et al. 197/98 3 7 7 l. [75] Inventors: Peter H. DeGratf, Newfield; James 32 5:2231 52 8;- Lee, Ithaca, 3,592,313 7/1971 Castle et a1. 197/98 x [73] Assignee, The National Cash Register 3,610,389 10/1971 Cortona et a1 197/14 X t 9 1 i Company Day on Ohio Primary Examiner-Ernest T. Wright, Jr. [22] Filed: Feb. 8, 1971 Attorney-Louis A. Kline, Wilbert Hawk, Jr. and [211 Appl. No: 113,430 George J. Muckenthaler 57 ABSTRACT [52] US. Cl. 197/107, l.97/98 A keyboard having magnetically actuated l.eed [51] Int. Cl B41 5/22 Switches and interposers swingable between the [58] Field of Search 197/12, 13, 14, 16, Switchesand adjacent magnets for opening and closing 197/171 1 187; the switches in response to key-operated mechanism. 235/145 146 Each interposer is supported from a pair/of spaced shafts which constitute a bail assembly, the spaced [56] 1 d f cued shafts being operable in rotary fashion about a common UNITED STATES PATENT center, and toothed racks are carried between the 3,189,153 6/1965 Barnard et al. 197/98 shafts and ngageable therewith to provide interlocking R26,954 9/1970 means for the keyboard. This interlocking means is of 3,493,092 2/1970 the non-entering type realizable by cooperation of 2.110.506 1933 the shafts with the racks being slidable therebetween, wherein, with one key depressed, depression of another 2:835:36) M1958 key tends to restore the first-mentioned key. 3,128,563 4/1964 2 Claims, 2 Drawing Figures 

1. In a printing machine having a carrier disengageably coupled to a driving means for displacement of the carrier along a print line from a starting position to a terminal position, a mechanism for yieldingly resisting the displacement of the carrier away from the starting position and for returning the displaced carrier thereto, said mechanism comprising: a frame having two spaced apart parallel guide rails forming a carrier accepting track extending parallel to the print line and for at least as long as the distance from the starting position to the terminal position, a carrier coupler straddling the rails of said track and guided thereby for displacement therealong and having a surface engageable by the carrier so as to be moved thereby along the track when the carrier is displaced away from the starting position, and a pair of similar compression type spring members lying in the plane of said frame on opposite sides thereof and each having one end pivotally connected to said frame and the other end pivotally connected to said carrier coupler, said spring members each having a free length greater than the distance between the pivotal connections of their ends with the frame and the carrier coupler when the carrier coupler is engaged by the carrier in said starting position, said spring members each being arcuately flexible and laterally extendible in the plane of the frame as the carrier moves the carrier coupler away from the starting position along the print line in engagement with the driving means, said spring members yieldingly urging the carrier and carrier coupler back toward the starting position of the carrier with substantially constant force and effectively transporting the carrier back to said starting position upon disengagement thereof from the driving means.
 2. A mechanism as defined in claim 1 further comprising a shock absorber positioned to be engaged by the carrier at the starting position thereof, said shock absorber being effective to statically urge the carrier in opposition to said spring members at the starting position and to resiliently resist overrun of the returning carrier beyond the starting position, said shock absorber comprising a shock transmitting member guided by said track for displacement therealong and a compression spring statically restrained at one end by the frame and seated at the other end on said shock transmitting member.
 3. In a printing machine having a carrier disengageably coupled to a driving means for displacement of the carrier along a print line from a starting position to a terminal position, a mechanism for yieldingly resisting the displacement of the carrier away from the starting position and for returning the displaced carrier thereto, said mechanism comprising: a frame having a carrier accepting track extending parallel to the print line and for at least as long as the distance from the starting position to the terminal position; a carrier coupler guided by said track for displacement therealong and having a surface engageable by the carrier so as to be moved thereby along the track when the carrier is displaced away from the starting position; a spring member having one end pivotally connected to said frame and the other end pivotally connected to said carrier coupler, said spring member having a free length greater than the distance between the pivotal connections of the ends of the spring member with the frame and the carrier coupler when said carrier coupler engages the carrier in said starting position, said spring member being arcuately flexible and laterally extendible as the carrier moves the carrier coupler away from the starting position along the print line in engagement with the driving means, said spring member yieldingly urging the carrier and carrieR coupler back toward the starting position of the carrier with substantially constant force and effectively transporting the carrier back to the starting position upon disengagement thereof from the driving means, and a shock absorber positioned to be engaged by the carrier at the starting position thereof, said shock absorber being effective to statically urge the carrier in opposition to said spring member at the starting position and to resiliently resist overrun of the returning carrier beyond the starting position, said shock absorber comprising a shock transmitting member guided by said track for displacement therealong and a compression spring statically restrained at one end by the frame and seated at the other end on said shock transmitting member.
 4. A mechanism as defined by claim 3 wherein said carrier accepting track is characterized by an elongated aperture extending through said frame, an extension of the carrier being inserted therein.
 5. A mechanism for biasing an object at a starting position and for returning the object from a displaced position to the starting position, said mechanism comprising: a frame including an aperture with two ends spaced apart at a substantially greater distance than the maximum distance between the displaced position and the starting position of the object, a guideway disposed along the length of said aperture, a stop obstructing said guideway, said stop being disposed at least as far from one end of the guideway as said maximum distance, and a spring anchor pin positioned on the frame adjacent to the one end of the guideway opposite from said stop, a coupler member displaceably movable within said guideway for guidance along said aperture between said stop and the one end of said guideway opposite from said stop, a spring anchor pin carried by the coupler member and extending generally parallel to the anchor pin positioned on the frame, a spring member having the opposite ends thereof pivotally connected to said anchor pins and having a free length greater than the distance between said anchor pins when the coupler member is at said stop, said spring member being operative to yieldingly bias said coupler member against said stop, and a shock absorber including a shock transmitting member also displaceably moveable within said guideway for guidance along said aperture on the opposite side of said stop from said coupler member, said shock absorber including also a compression spring having one end statically disposed against said frame and a free end positioned in abutment with said shock transmitting member for resiliently receiving the returning object and for urging the object in a direction opposing said spring member and back into said biased starting position.
 6. A mechanism as defined in claim 5 wherein said spring member comprises a first spiral spring having an extendible bowed portion projecting outwardly from one side of said frame.
 7. A mechanism as defined in claim 6 additionally comprising a second spiral spring similarly having an extendible bowed portion projecting outwardly from an opposite side of said frame from said first spiral spring.
 8. A constant force carrier return mechanism including, in combination: a supporting frame having two parallel guide rails forming a track, a stop positioned at the same location on each guide rail intermediate the ends thereof, the space between the guide rails and the stops being free of obstruction, a first coupler member bridging the guide rails and guided for movement thereby along that section of the track on one side of the stops, and a second coupler member similarly bridging the guide rails and guided for movement thereby along that section of the track on the other side of the stops, said first and second coupler members being shaped to engage opposite sides of a carrier introduced into the space between the guide rails and each coupler member being moved by the carrier along that section of the track upon which the coupler member is guided when the carrier moves in the direction of the coupler member and away from the stops, at least one spring member connected at one end to the first coupler member and connected at the other end to the supporting frame adjacent to the end of the track section along which the first coupler member is movable, each said spring member being spirally wound into a coil for part of the length thereof and exhibiting an arcuate formation having a relatively large radius of curvature when the first coupler member is abutting the stops, the radial curvature of the arcuate formation of each said spring member progressively decreasing as the ends of the spring member approach one another and progressively increasing the lateral deflection of the middle portion thereof during motion of the first coupler member away from the stops and such that the spring member exerts a substantially constant force on the carrier in any position of movement of said carrier member along the track section of the first coupler member, and a shock absorbing assembly associated with said second coupler member including at least one compression spring yieldingly urging the second coupler member against said stops but being effective to yieldingly absorb the inertia of the carrier when the carrier overruns the position of the stops on return motion of the carrier along the track.
 9. A constant force carrier return mechanism including, in combination: a supporting frame having two spaced apart parallel guide rails forming a track, stops positioned at the same location in the guide rails and cooperating to represent a starting position for a mechanism supporting carrier introduced between the guide rails for displacement in either direction along the track and from one side to the other side of the stops, a coupler member straddling the guide rails and being guided thereby for displacement therealong away from said starting position and being engageable and jointly movable by the mechanism supporting carrier when the carrier is displaced along the guide rails in the same direction away from said starting position, at least one spring member having the middle portion thereof in the form of a spirally wound coil such that when the ends of the spring member are drawn toward one another the middle portion thereof will progressively distend laterally in the form of an arc while accompanied by a progressive decrease in the radius of curvature of the arc such that the spring member resists such change in the arc formation with a substantially constant force, means connecting one end of each such spring member to a fixed support and the other end to the coupler member leaving the balance of the spring member free for said lateral arcuate distention relative to the carrier return mechanism, whereby displacement of the coupler member by mechanism supporting carrier away from the starting position will be opposed by a substantial constant force throughout such movement along the track, and a shock absorbing assembly including a second coupler member interposed in the path of travel of said mechanism supporting carrier adjacent to said starting position and being jointly movable away from the starting position by the carrier when the carrier on return movement thereof overruns said starting position, and further including resilient means yieldingly resisting any such displacement of said second coupler member caused by the overrun of the carrier and being effective to return the second coupler member and the carrier back to the starting position. 